The German reference DE-PS 694 029 discloses a hydraulic adjustment device using a ship's screw propeller drive to adjust the propeller blades. The hydraulic fluid used here, usually oil, is conducted to the shaft in the interior of the ship. However, the seal in the area of the rotation passage always is a point of special risk. Possible leaks in this area can entail considerable consequences, especially when used for turbines or pumps. A lack of tightness in the passage would cause an impermissible mixing of hydraulic fluid with the transport medium. To prevent this, infeed devices are usually disposed in chambers which require special sealing.
Another solution is disclosed in EP-PS 0 174 286 which provides for the components of a hub lining which cross the flow chamber of the transport medium to conduct the hydraulic fluid to the variable-pitch propeller. The transfer from the stationary to the rotating part then takes place within the hub lining. However, this solution is very prone to trouble in cases where the transport media are contaminated by fibrous or granular components. These components can impede the flow to or from the rotor disk, substantially increasing the likelihood that the unit will break down.